//
//  FFAES.m
//  FFAirUtilEncrypt
//
//  Created by chewyong on 2017/6/5.
//  Copyright © 2017年 isoftstone. All rights reserved.
//

#import "FFAES.h"
#import <CommonCrypto/CommonCryptor.h>

@implementation FFAES

/**
 * 加密
 * @param data 需要加密的数据NSData
 * @param key 加密的秘钥
 * @return 加密后的数据
 */
+ (NSData *)encrypt:(NSData *)data key:(NSString *)key{
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES128+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    if (key.length>kCCKeySizeAES128) {
        key = [key substringToIndex:kCCKeySizeAES128];
    }
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [data length];
    
    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES128,
                                          NULL /* initialization vector (optional) */,
                                          [data bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;

}

/**
 * 解密
 * @param data 需要解密的数据NSData
 * @param key 解密的秘钥
 * @return 解密后的数据
 */
+ (NSData *)decrypt:(NSData *)data key:(NSString *)key{
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES128+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    if (key.length>kCCKeySizeAES128) {
        key = [key substringToIndex:kCCKeySizeAES128];
    }
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [data length];
    
    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES128,
                                          NULL /* initialization vector (optional) */,
                                          [data bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesDecrypted);
    
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;
}


@end
